Flow cell optical detection system

ABSTRACT

The present invention discloses a flow cell optical detection system comprising a light source, a flow cell and a light detector, wherein the light detector is arranged in a separate detector unit that is arranged to be releasably attached to a detector interface, the detector interface being in optical communication with the light source and comprises optical connectors for optically connecting the flow cell and the detector unit in the light path from the light source, and wherein the flow cell is an interchangeable unit arranged to be held in position by the detector unit when attached to the detector interface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a filing under 35 U.S.C. §371 and claims priority tointernational patent application number PCT/SE2009/051321 filed Nov. 23,2009, published on May 27, 2010 as WO 2010/059121, which claims priorityto U.S. provisional patent application Ser. No. 61/117,261 filed on Nov.24, 2008.

FIELD OF THE INVENTION

The present disclosure relates to a flow cell optical detection systemof modular design.

BACKGROUND OF THE INVENTION

Flow cell optical detection system, typically comprises a light sourcefor providing light of one or more wavelengths to a fluid sample in afluid cell and an optical detection system for detecting any interactionbetween the light and the sample. One example of a flow cell opticaldetection system is a flow cell UV absorption monitor system that isutilized to measure different absorbance of light at various wavelengthsin chromatography systems when separated molecules are eluted from thecolumns.

Monitor systems of this type usually include a light source, a flow celland a light detector. Ideally, the flow cell is designed to ensure asignal-to-noise ratio with minimal drift and refractive indexsensitivity. However, in some systems the flow cell is externallyconnected to the light source with optical fibers, whereby it becomessensitive to external light, temperature difference and movements (e.g.vibrations). The optical fibers are also very fragile and can be crackedif bended. This vibration and temperature fluctuation may lead toproblems with the operation of the monitor. Also, the monitors aretypically built as one unit where both light source and detector arecombined in the same housing. This limits the flexibility of the systemand might also give electromagnetic compatibility problems since thelight source and sensitive detector electronics are placed in the samehousing.

SUMMARY OF THE INVENTION

The object of the invention is to provide a new flow cell UV absorptionmonitor system, which overcomes one or more drawbacks of the prior art.This is achieved by the flow cell UV absorption monitor system asdefined in the independent claim.

One advantage with such a flow cell UV absorption monitor system is thatit is easy to switch the interchangeable flow cell preservingreproducible measurement results at the same time as it is simple toreplace the detector unit if needed.

Another advantage is that the detector unit may be located at a remotelocation with respect to the light source.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specific exampleswhile indicating preferred embodiments of the invention are given by wayof illustration only. Various changes and modifications within thespirit and scope of the invention will become apparent to those skilledin the art from the detailed description below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a schematic of a typical multi-wavelength monitor.

FIGS. 2A to 2D show a schematic flow cell optical detection system inaccordance with an embodiment of the invention.

FIG. 3 shows a flow cell optical detection system in accordance withanother embodiment of the invention.

FIG. 4 shows a detector housing, a flow cell and a monochromator housingin accordance with an embodiment of the invention.

FIG. 5 shows a detector housing connected by the flow cell to amonochromator of FIG. 2 in accordance with an embodiment of theinvention.

FIG. 6 shows a schematic of a section cut of the detector housing andthe monochromator of FIG. 2 in accordance with an embodiment of theinvention.

FIG. 7 is a schematic of connecting parts in a fiber system of thedetector housing, UV Cell and the monochromator in accordance with anembodiment of the invention.

FIGS. 8A and 8B illustrate the movement of the optical fiber of FIG. 5in accordance with an embodiment of the invention.

FIGS. 9A and 9B shows a schematic of the optical fiber system in anexternal view and internal view.

DETAILED DESCRIPTION OF THE INVENTION

The presently preferred embodiments of the invention are described withreference to the drawings, where like components are identified with thesame numerals. The descriptions of the preferred embodiments areexemplary and are not intended to limit the scope of the invention.

FIG. 1 illustrates a typical multi-wavelength Ultra-violet (UV)-Visiblemonitor. This monitor 101 includes an interchangeable flow cell 103 andoptical fibers 105. Monitor 101 may e.g. be a Monitor UV-900manufactured by GE Healthcare, Life Sciences located in Uppsala, Sweden.This monitor utilizes advanced fiber optic technology to monitor lightwith high sensitivity at up to three wavelengths simultaneously in arange of 190-700 nm. The use of fiber optics together with the uniqueflow cell design ensures a signal-to-noise ratio with minimal drift andrefractive index sensitivity. Typically, the monitor 101 includes amonochromator 107 with a light source (not shown), such as a xenon flashlamp (not shown) that provides a high intensity, continuous spectrum oflight, and a tuneable monochromator arrangement (not shown) forselecting the wavelength of light output to the fiber 105. The lamp isactivated only during the chromatographic run, ensuring that its longlifetime of approximately 4000 hours of effective operation is usedefficiently. In the disclosed monitor 101, the optical fiber 105 opticsleads the light from the monochromator 107 to an optical splitter unit109 splitting the light to a reference fiber 111 and a flow cell fiber113 leading directly to the flow cell 103 and focus its full intensityon the liquid flow path, thus maximizing the sensitivity of themonitoring. Flow cell 103 may have any path length, such as a pathlength of 2 mm and cell volume of 2 μl or path length of 10 mm and acell volume of 8 μl. The transmitted light through the flow cell 103 isguided to a light detection unit 115 detector (not shown) via an opticalfiber 121. The light detection unit 115 has a flow cell input 119connected to fiber 121 and a reference input 117 connected to thereference fiber 111. The detection unit 115 further may comprisesuitable processing means for comparing the flow cell input with thereference to detect changes in light absorption in the flow cell.

According to one embodiment shown in FIG. 2, there is provided a flowcell optical detection system 100 comprising a light source 107, a flowcell 201 and a light detector 205, wherein the light detector isarranged in a separate detector unit 201 that is arranged to bereleasably attached to a detector interface 215 a. The detectorinterface 215 a being in optical communication with the light source 107and comprises optical connectors 221, 219 for optically connecting theflow cell 211 and the detector unit 201 in the light path from the lightsource 107. The flow cell 211 is an interchangeable unit arranged to beheld in position by the detector unit 201 when attached to the detectorinterface 215 a.

As mentioned above the optical detection system 100 may be an UV-Visiblespectrometer monitor. In such embodiments, the light source may be atuneable monochromatic light source as disclosed schematically above,and referred to as a monochromator 107. In alternative embodiments, thelight source 107 may be a non tuneable monochromatic light source, suchas a laser diode of suitable wavelength or the like. In otherembodiments the light source may be a polychromatic light source.

The detector interface 215 a may be a section of a monitor housing 101as is schematically indicated in FIG. 2A, but it may be arranged remoteto the light source 107 etc. In the disclosed embodiment the detectorinterface 215 a is optically connected to the source of light 107 by asample illumination fiber 113 and a reference fiber 111, and thedetector unit is arranged to detect the relative difference between thesample illumination light after the flow cell 211 and the reference bymeans of photo detectors 205 and 203, respectively. The photo detectors203 and 205 may be of any suitable type capable of detecting light ofthe selected wavelength, such as photo diodes or the like. In oneembodiment, the photo detectors are provided as a matched pair.

In one embodiment, the flow cell 211 is optically connected to thedetector unit 201 by a fixed connector, and to the detector interface215 a by a self adjusting optical connector 221. In the disclosedembodiment, the detector interface is optically connected to the sourceof light by one or more optical fibers. But in alternative embodiments(not shown), the detector interface may be a section of a monitorhousing (schematically indicated by ref 101) and the light from thelight source 107 is output directly to the connector 221 and into theflow cell without passing an optic fiber.

FIG. 2B shows the optical detection system 100 of FIG. 2A wherein theDetector unit 201 and the flow cell 211 are detached from the detectorinterface 215 a. FIG. 2C shows a schematic cross section of a flow cell211 in accordance with one embodiment of the present invention. The flowcell 211 comprises optical connectors 213 and 209 and a fluid inlet 242and a fluid outlet 241 for connecting the flow cell 211 to a fluidicsystem for providing the sample fluid flow in a measurement cell 240.Light is supplied into the measurement cell 240 via light guide 243 andis collected by light guide 244 which in turn transmits the collectedlight to the sample photodiode 205.

FIG. 3 discloses an alternative embodiment of the optical detectionsystem 100, wherein the detector unit 201 is integrated with thedetector interface and comprises an optical splitter 109 b unit fordiverting reference light to the reference photo detector 203 from thelight supplied by the light source via fiber 105. In this embodiment,the flow cell 211 is releasably attached to the detector unit by meansof connector groves 232. Moreover, the detector unit is schematicallydisclosed as being arranged remotely to the light source etc,interconnected to the light source by the optic fiber 105 and in remotecommunication with a system controller 250 or the like by wire 251.According to one embodiment, the detector unit 201 may comprise onedetector and a beam-chopper to alter which beam that illuminates the onedetector.

The light source, such as a monochromator unit, is delicate and need tobe placed in a stable and vibration free environment, whereas thedetection unit may be a rigid solid state unit that is capable of beingplaced at more exposed positions, remote to the monochromator unit. Thismay be beneficial in situations where it is desired to performmeasurements close to process equipment or the like.

According to other embodiments, the detector interface 215 a may bearranged as a section of an external face of a monitor housing.

FIG. 4 shows an example of a new detector 201, a flow cell 211 and partsof a monitor or monochromator housing 215. The monitor housing 215 maybe referred to as a second housing. The detector or detector housing 201or a first housing includes: a reference photo diode 203, a sample photodiode 205 and a locking mechanism 207. Next to the detector housing 201is an interchangeable flow cell 211; this flow cell 211 has an opticaloutput end, herein referred to as the top portion, that includes a firstfiber connector 209 and an optical input end, herein referred to as thebottom portion, of the interchangeable flow cell 211 that includes asecond fiber connector 213. Fiber connector 213 may have any type ofshape, such as a cylindrical or a conical shape. Adjacent to theinterchangeable flow cell 211, there is the monitor housing 215 thatincludes the following components: a reference fiber 219, a sample fiber221, an electrical cable connector 223 with a floating electricalconnector and a floating connector 217. The floating connector 217 is afloating, spring loaded splicing adaptor. Reference fiber 219, and asample fiber 221 are precisely aligned in their connectors of thehousing 215. In another embodiment of the invention, the flow cell 211may not be directly attached to the monochromator. The flow cell 211only needs an optical fiber to guide light from the optical fiberconnector 221.

In the disclosed embodiment the detector 201 comprises detectorelectronics 230 arranged to collect and optionally evaluate the outputfrom the reference photodiode 203 and the sample photodiode 205. Thedetector electronics 230 are arranged to communicate with a main controlsystem or other data collection system via the connector 223.

The top portion 209 of the interchangeable flow cell 211 engages a holeor a receptacle 205 a of the sample photo diode 205 of the detectorhousing 201. The top portion 209 of the interchangeable flow cell 211has a fixed position. Next, the bottom portion 213 of theinterchangeable flow cell 211 is movably inserted into a receptacle 217a or a hole of the splicing connector 217 of the monitor housing 215. Inorder for the top portion 209 of the interchangeable flow cell to engagethe sample photo diode 205, there is an alignment between the topportion 209 and the narrow bore receptacle 205 a.

The bottom portion 213 of the interchangeable flow cell 211 is guided atfirst with a conical shaped entrance or receptacle 217 a of a floatingsplice adaptor 217 of the monitor housing 215. The splicing connector217 utilizes its spring-loaded mechanism to move itself in or out ofposition in order to receive the bottom portion 213 and also to meet thesample fiber 221. The sample fiber 221 may be referred to as opticalfiber connector 221. Sample fiber 221 and its floating splicing adaptoralso moves in an x, y, z direction and sample fiber 221 moves a certainangle in the range of 0 to 10 degrees. Also, the sample fiber 221 may bemoved along a z direction, in the range 0 mm to 2 mm. The sample fiber221 and its floating splicing adaptor 217 move in the x, y, and zdirections and move a certain angle in order to meet the bottom portion213 of the UV cell 211. The splice connector 217 moves in the leftsideway, right sideway, up and down directions or at a tilted angle from0 to 10 degrees. This left sideway or right sideway movement is +/−0.3mm. For example, the splice connector 217 moves in a z direction by aspring at the splice connector 217 that brings the splice connector 217forward towards the interchangeable flow cell 211. The movement in the zdirection is to ensure that the distances between the fibers are correctin the splice connector 217 in spite of different lengths of the flowcell 211 with its connectors 213 and 209. After the bottom portion ofthe flow cell 211 is secured to the monitor housing 215, then thedetector housing 201 is secured to the monitor housing 215 by thelocking mechanism 207 as shown in FIG. 5.

FIG. 6 shows a schematic section cut of the detector 201, the flow cell211 and the monitor housing 215. At this view, the flow cell 211 islocated in between the detector housing 201 and the monitor housing 215.Specifically, the top portion 209 of the flow cell 211 is in thedetector housing 201 and the bottom portion 213 of the flow cell 211 isin the monitor housing 215. In the disclosed embodiment, the flow cellcomprises a fluid inlet 242 and a fluid outlet 241 for connecting theflow cell 211 to a fluidic system for providing the sample fluid flow ina measurement cell 240. Light is supplied into the measurement cell 240via light guide 243 and is collected by light guide 244 which in turntransmits the collected light to the sample photodiode 205.

FIG. 7 is a schematic of connecting parts in the fiber system of themonitor housing and the UV cell of FIG. 4. The monitor housing 215includes: a fiber connector 221, a floating splicing adaptor 217 and aspring 225 located outside of the floating splicing adaptor 217. The UVcell 211 or flow cell includes a fiber connector 213. As shown in FIG.8A, fiber splicing adaptor 217 moves in an x, y, z direction and thefiber splicing adaptor 217 also moves a certain angle, a, in the rangeof 0 to 10 degrees (FIG. 8B). Also, the fiber splicing adaptor 217 maybe moved along a z direction as in FIG. 8A. The fiber connector 213moves splicing adaptor 217 in the x, y, and z directions and moves acertain angle in order to meet the fiber connector 213.

The connector 213 of the UV cell 211 is shaped or configured to fit intothe floating splicing adaptor 217 and meet the fiber connector 221 at adistance of 0.01 mm to 0.1 mm. A movement of the UV cell and itsconnector 213 in the X, Y and Z directions and in a tilting motion of 0to 10 degrees allows it still to fit into the floating splicing adaptor217 of the monitor housing 215. The fiber splicing adaptor 217 has afloating part that is spring loaded to allow fiber connector 221 to movein several different directions, as discussed above, between the UV cell211 and the monitor housing 215 to ensure that the fiber connectors 213and 221 are at a correct distance. The floating splicing adaptor 217enables the UV cell 211 to be easily inserted into the monitor housing215.

FIG. 9A shows a schematic of the detector housing and flow cellassembled to the monitor housing with no visible fibers. In this figure,the UV cell 211 is inserted in between the detector housing 201 and themonitor housing 215. In order to secure the fiber connector 213 in thefloating splicing adaptor 217 the latch mechanism 207 is used as anexternal force. FIG. 9B shows the connector 213 inserted in the floatingsplicing adaptor. The floating splicing adaptor 217 and its spring 225adjusts its position so the fiber connector 221 can receive the fiberconnector 213 of the UV cell 211 at a correct position and distance.

This embodiment provides an apparatus that enables a user to easilyremove and change a flow cell located there between monitor housing anddetector housing. Also, this invention protects sensitive optical fiberand detector electronics, which minimizes disturbances to the opticalfiber and detector electronics. Further, this embodiment provides theuser with a solution that is a fast and easy to assemble or disassemblea UV cell from a monochromator and a detector housing without any tools.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that this is done by way ofillustration and example only and is not to be taken by way oflimitation. The scope is to be limited only by the terms of the appendedclaims.

What is claimed is:
 1. A flow cell optical detection system withdetachable units and optical connectors, comprising: a first detachableunit including a housing, an interface mounted thereon, and a lightsource, wherein the light beam from the light source are split into afirst light beam and a second light beam by an optical splitter to gothrough a first optical path in the system and a second optical path inthe system respectively; a second detachable unit including a firstdetector on the first optical path, wherein the second unit isdetachable from the first unit; and a liquid flow cell including a firstunit connector; wherein the detachable units and the flow cell areconfigured to provide (i) a first optical connection between the lightsource and the first detector following the first optical path and (ii)a second optical connection between the light source and the flow cellfollowing the second optical path when the first unit is releasablyattached at the interface to the second unit with the flow cellsandwiched in between the first unit and the second unit; and whereinthe second optical connection is provided by the engagement of the firstunit connector of the flow cell and a connector of the first unitincluded in the interface.
 2. The system of claim 1, wherein the secondunit includes a second detector on the second optical path.
 3. Thesystem of claim 2, wherein the flow cell is optically connected to thesecond detector along the second optical path when the first unit isreleasably attached to the second unit.
 4. The system of claim 1,wherein the first unit connector is a self-adjusting optical connector.5. The system of claim 4, wherein the self-adjusting optical connectoris a spring-loaded splicing adaptor.
 6. The system of claim 1, whereinthe first light beam is a reference light beam and the first detector isassociated with the reference light beam from the light source throughthe first optical path.
 7. The system of claim 2, wherein the secondunit includes electronics configured to process signals from the firstand second detectors.
 8. The system of claim 7, wherein the electronicsis configured to compute a difference between signals from the first andsecond detectors.
 9. The system of claim 1, wherein the light source isconfigured to output one of ultraviolet light and visible light.
 10. Thesystem of claim 3, wherein the second light beam is a sample light beamand the second detector is associated with the flow cell and the samplelight beam from the light source through the second optical path. 11.The system of claim 1, wherein the flow cell further comprising a secondunit connector and the second optical connection further comprises thesecond unit connector releasably engaged with a connector on the secondunit such that the flow cell is sandwiched in between the units when thefirst unit is releasably attached at the interface to the second unitand the flow cell is optically connected to the second detector alongthe second optical path.
 12. The system of claim 11, wherein the firstunit connector and the second unit connector are fiber connectors. 13.The system of claim 1, wherein the first optical connection is providedthrough the engagement of a first optical path connector of the firstunit on the interface with a counterpart connector of the second unit.14. A flow cell optical detection system with detachable units andoptical connectors, comprising: a first detachable unit including ahousing, an interface mounted thereon, an optical path connector of thefirst unit on the interface, a flow cell connector on the interface, anda light source, wherein the light beam from the light source are splitinto a first light beam and a second light beam by an optical splitterto go through a first optical path in the system and a second opticalpath in the system respectively; a second detachable unit including afirst detector on the first optical path, a second detector on thesecond optical path, an optical path connector of the second unit, and aflow cell detector of the second unit, wherein the second unit isdetachable from the first unit; and a detachable liquid flow cellincluding a first unit connector and a second unit connector, whereinthe flow cell is detachable from the first and the second units; whereinthe detachable units and the flow cell are configured to provide (i) afirst optical connection between the light source and the first detectorfollowing the first optical path and (ii) a second optical connectionbetween the light source and the flow cell following the second opticalpath when the first unit is releasably attached at the interface to thesecond unit with the flow cell sandwiched in between the first unit andthe second unit; wherein the first optical connection is providedthrough the engagement of the optical path connector of the first uniton the interface with the optical path connector of the second unit,wherein the second optical connection is provided by the engagement ofthe first unit connector of the flow cell and the flow cell connector ofthe first unit and the second unit connector of the flow cell with theflow cell connector of the second unit such that the flow cell issandwiched between the units when the first unit is releasably attachedto the second unit and the flow cell is optically connected to thesecond detector along the second optical path, and wherein the secondunit connector is an optical fiber connector and the first unitconnector is a self-adjusting optical connector.
 15. The system of claim14, wherein the self-adjusting optical connector is a spring-loadedsplicing adaptor.
 16. The system of claim 14, wherein the first lightbeam is a reference light beam and the first detector is associated withthe reference light beam from the light source through the first opticalpath and the second light beam is a sample light beam and the seconddetector is associated with the flow cell and the sample light beam fromthe light source through the second optical path.
 17. The system ofclaim 14, wherein the second unit includes electronics configured toprocess signals from the first and second detectors to compute adifference between signals from the first and second detectors.
 18. Thesystem of claim 14, wherein the light source is configured to output oneof ultraviolet light and visible light.
 19. A flow cell opticaldetection system with detachable units and optical connectors,comprising: a first detachable unit including a housing, an interfacemounted thereon, an optical path connector of the first unit on theinterface, a flow cell connector on the interface, and a light source,wherein the light beam from the light source are split into a firstlight beam and a second light beam by an optical splitter to go througha first optical path in the system and a second optical path in thesystem respectively; a second detachable unit including a first detectoron the first optical path, a second detector on the second optical path,an optical path connector of the second unit, and a flow cell detectorof the second unit, wherein the second unit is detachable from the firstunit; and a detachable liquid flow cell including a first unit connectorand a second unit connector, wherein the flow cell is detachable fromthe first and the second units; wherein the detachable units and theflow cell are configured to provide (i) a first optical connectionbetween the light source and the first detector following the firstoptical path and (ii) a second optical connection between the lightsource and the flow cell following the second optical path when thefirst unit is releasably attached at the interface to the second unitwith the flow cell sandwiched in between the first unit and the secondunit; wherein the first optical connection is provided through theengagement of the optical path connector of the first unit on theinterface with the optical path connector of the second unit, whereinthe second optical connection is provided by the engagement of the firstunit connector of the flow cell and the flow cell connector of the firstunit and the second unit connector of the flow cell with the flow cellconnector of the second unit such that the flow cell is sandwichedbetween the units when the first unit is releasably attached to thesecond unit and the flow cell is optically connected to the seconddetector along the second optical path, wherein the first unit connectoris spring-loaded splicing adaptor, and wherein the light source isconfigured to output one of ultraviolet light and visible light and thesecond unit includes electronics configured to process signals from thefirst and second detectors to compute a difference between signals fromthe first and second detectors.
 20. The system of claim 14, wherein thefirst light beam is a reference light beam and the first detector isassociated with the reference light beam from the light source throughthe first optical path and the second light beam is a sample light beamand the second detector is associated with the flow cell and the samplelight beam from the light source through the second optical path.